1. Field of the Invention
The present invention relates to an optical switch device that controls the angular displacement of micro mirror structures, eliminates the interference of magnetic field from other optical switch device and controls the horizontal displacement of micro mirror structures to prevent vibration and collision in the optical switch device transportation. Further, the present invention is directed to control the displacement and eliminate the interference of micro mirror structures or a plurality of optical switch devices. Alternatively, the present invention also improves the reliability of transporting optical switch devices.
2. Description of the Related Art
Recently several researchers have spurred an increasing development of microstructures in optical communication and micro electro-mechanical systems (MEMS). The microstructures that were not performed in the past are fabricated by a combination of silicon deposition, surface micromachining and bulk-micromachining. A typical optical communication system requires a number of small-sized, high-speed, and highly reliable optical switches for the line switching operation in any applications. The optical switch devices are discussed in detail in Transducers, 1995, entitled xe2x80x9cAn electrostatically operated torsion mirror for optical switching devicexe2x80x9d by Hiroshi Toshiyoshi and Hiroyuki Fujita and in Solid-state sensor and actuator, 1998, entitled xe2x80x9cParallel assembly of hinged microstructures using magnetic actuationxe2x80x9d by Yang Yi and Chang Liu. Recently, U.S. Pat. Nos. 6,094,293 and 5,960,132 have been disclosed the related information.
The optical switch devices as mentioned previously use electrostatic or magnetic force to control the angular displacement of individual mirror. The incident light is transmitted and passed only when mirror is in the non-reflection state (OFF-state). On the other hand, the incident light is reflected and changed the origin route when the mirror moves between the non-reflection state and the reflection state (On-state). A problem associated with the typical optical switch devices is that precision alignment of mirror is required to control the reflective light""s route. The mirror achieves large angular displacements (over 90xc2x0) under a torque provided by applying an external magnetic or electrostatic force because the mirror is influenced by the inertia.
FIG. 1 and FIG. 2 show the 3D views and cross-section views of the micro mirror in the prior art. A torsion mirror device 10 is formed on a flat surface of a silicon substrate 11 (or glass substrate). The torsion mirror device 10 includes a bump 15, a reflective mirror 14 and a torsion bar 121 connected the reflective mirror 14 with the first connector section 12a and the second connector section 12b. 
Alternatively, first connector section 12a, second connector section 12b, the torsion bar 121, the reflective mirror 14, and the bump 15 are formed by the elastic poly-silicon in the lithography process. The first connector section 12a and second connector section 12b are performed on the silicon substrate 11 and separated by the torsion bar 121. The reflective mirror 14 is formed on the extension part of the middle of the torsion bar 121. A magnetic material 141 (so called permalloy) is performed on the top of the reflective mirror 14. The permalloy 141 is deposited by the way of sputtering or electroplating. The reflective mirror 14 contains a reflective area 142. The reflective area 142 is performed by a smooth plane, which makes the incident light to change the route of the incident light when the incident light approaches the reflective area 142. The bump 15 fixed under the reflective mirror 14 is a square or a rectangle. Furthermore, the height of the bump 15 is suitable for the reflective mirror 14 placed on the bump 15 when the reflective mirror 14 is in the horizontal level. An actuator 16 under the silicon substrate 11 could provide repulsive force to raise the reflective mirror 14.
The conventional rotation mechanism of the reflective mirror 14 is introduced in FIGS. 3-5. As shown in FIG. 3, the torsion mirror device 10 is at rest and the external magnetic field is just applied to the actuator 16. FIG. 4 shows that a torque provided by the actuator 16 makes the torsion mirror device 10 rotate from the horizontal level to vertical level. Thereafter, FIG. 5 shows that the torsion mirror device 10 achieves large angular displacements (over 90xc2x0) and doesn""t keep stable at the vertical position under the influence of the inertia.
As shown in FIG. 3, when the actuator 16 applying magnetic field results in flux density 161 and the permalloy 141 induces magnetization 163. The positive pole of the flux density 161 and the positive pole of the magnetization 163 result in repulsive force 164. The repulsive force 164 raises the reflective mirror 14 away from silicon substrate 11. Alternatively, the torsion bar 121 which connects with the reflective mirror 14, first connector section 12a and second connector section 12b. When the reflective mirror 14 rotates from the horizontal level to the vertical level, the torsion bar 121 is provided with elasticity to distort under the repulsive force 164. Furthermore, the repulsive force 164 achieves the maximum when the distance between the positive pole of the flux density 161 and the positive pole of the magnetization 163 is shortest.
As shown in FIG. 4, the repulsive force 164 achieves smaller when the distance between the positive pole of the flux density 161 and the positive pole of the magnetization 163 is farther. The torsion bar 121 is so elastic that the reflective mirror 14 moves forward to the vertical position.
As shown in FIG. 5, when the reflective mirror 14 approaches the vertical position, the distance between two positive poles increases further and the repulsive force 164 decreases substantially. The repulsive force 164 approaches zero when the reflective mirror 14 is at a vertical position 17. In the influence of the inertia, the reflective mirror 14 stops at a static position 18 after the orientation mirror 14 rotates over the vertical position 17. The repulsive force 164 is continuously applied to retain the reflective mirror 14 at the static position 18.
FIG. 6 illustrates a cross-section view that the conventional mirror device stays at the static position 18. Although the actuator 16 is not provided by applying external magnetic field anymore, the induced magnetic filed of the permalloy 141 disappears and the reflective mirror 14 influenced by resilience moves back to horizontal level form the static position 18. FIG. 7 shows a cross-section view that the conventional torsion mirror device 10 moves back to the horizontal level. A problem with a reflective mirror 14 similarly described above is that the reflective mirror 14 couldn""t retain the horizontal level for the inertia when the reflective mirror 14 moves back. The bump 15 overcomes the problem because the height of the bump 15 is suitable for the reflective mirror 14 stopped on the bump 15.
As shown in FIG. 7, the torsion mirror device 10 isn""t fixed by the bump 15 in the horizontal level when the torsion mirror device 10 or an array of torsion mirror devices is transported.
FIG. 8 illustrates the cross-section view of an array of torsion mirror devices 20 in prior art. The array of torsion mirror devices 20 are composed by the sixteen micro mirrors labeled 211, 212, 213, 214, 221, 222, 223, 224, 231, 232, 233, 234, 241, 242, 243 and 244. Among these mirrors, the mirrors labeled 213, 221, 232 and 244 are in the vertical level (reflective state), and therefore beams of incident light 20A, 20B, 20C and 20D are individually reflected by the mirrors labeled 213, 221, 232 and 244 to sensors of 20E, 20F, 20G and 20H. The other mirrors labeled 211, 212, 214, 222, 223, 224, 231, 233, 234, 241, 242 and 243 are set to in the horizontal level. Alternatively, the actuators of the mirrors labeled 213, 221, 232 and 244 are provided by the external magnetic field to retain the mirrors in the vertical level. The other problem is that the actuators described above influence some of the mirrors labeled 211, 212, 214, 222, 223, 224, 231, 233, 234, 241, 242 and 243 so that these mirrors don""t retain in the horizontal level. Prior art array of torsion mirror devices 20 could not operate properly if incident or reflective light is obstructed by mirrors not remaining in horizontal position. The present invention proposes an interference eliminator to resolve the above-mentioned problems.
According, it is a primary object of the present invention is to provide a torsion mirror device or an array of torsion mirror devices, which can positively be retained in the vertical level.
It is another object of the present invention is to provide a torsion mirror device or an array of torsion mirror devices, which can positively be retained in the horizontal level.
It is yet another object of the present invention is to provide a torsion mirror device with function of eliminating magnetic interference, which comes from other torsion mirror device.
To achieve these objects, a system of angular displacement control for micro mirror includes a stationary vertical element, a stationary horizontal element and an interference eliminator. Alternatively, the stationary horizontal element fixes micro mirrors in the transportation to avoid vibrating and colliding. The stationary vertical element orientates the micro mirrors in the vertical position. The interference eliminator eliminates from magnetic interference affecting the operation of the micro mirrors. The micro mirrors with interference eliminators aren""t affected by other micro mirrors in the operation process.